Conservationists have declared a win in a fight over Tasmania’s takayna/Tarkine rainforest after a judge found the Morrison government had erred in approving preliminary work on a mining waste dam.
Federal court justice Mark Moshinsky found the then environment minister, Sussan Ley, had failed to apply the precautionary principle before allowing drilling and surveying works for a new tailings dam near the town of Rosebery, on the state’s west coast.
In a judgment late on Monday, Moshinsky said a decision in January by an environment department official representing Ley had not considered whether the works would cause serious or irreversible damage to the habitat of the endangered Tasmanian masked owl.
The justice did not make any immediate orders, but flagged the approval was likely to be set aside. That could mean the proposal by minerals company MMG would need a new assessment under national environment laws.
The Bob Brown Foundation said the judgment was one of the most significant in environmental law since the Environment Protection and Biodiversity Conservation Act was introduced in 1999, as it showed the precautionary principle must be employed when the effects of a proposed development were unclear.
The foundation’s campaign manager, Jenny Weber, said the masked owl – which is listed as endangered in Tasmania, and is believed to have been reduced to about 500 breeding pairs – was “not considered at all” in the approval decision.
“This decision tells miners, loggers and other big project proponents that they can no longer profit from the uncertainty that follows a lack of quality scientific investigation,” she said.
Neither MMG nor the Tasmanian government, which is a strong supporter of the development, had responded to Guardian Australia before publication.
The validity of the federal approval of the drilling and roadworks was already under question after Ley agreed before the election that there were grounds for it to be formally reconsidered. Responsibility for that process was handed to the new environment minister, Tanya Plibersek, after Labor won the election. She is yet to make a decision.
Bob Brown, the former Greens leader who started the foundation, said the judgment was huge and would bolster Plibersek’s hand “in defending threatened species from the Tarkine to Cape York to the Burrup Peninsula”.
He said the commonwealth should compensate nearly 100 protesters who had been arrested while campaigning against the development.
In a statement on Tuesday morning, Plibersek said the legal action concerned a decision made under the previous federal government, that she had been notified of the judgment and would consider it in detail.
The majority-Chinese owned company says a new tailings dam is needed to extend the life of its 85-year-old zinc, copper and lead Rosebery mine. If the dam is approved, the company expects to clear up to 285 hectares – roughly equivalent to 350 football pitches – of rainforest and other terrain for the dam and a 3.5km pipe that would carry toxic waste from the mine across the Pieman River.
The Bob Brown Foundation says crossing the river would place the tailings dam inside the Tarkine, an environmentally diverse area that the Australian Heritage Council 10 years ago recommended should be protected. It says there are other options open to MMG.
The justice reserved his orders until a hearing expected later this week.
